FD140 is a 4-port E1/T1/BRI interface failover appliance. It can better protect the unpredictable problems happen to the Asterisk PBX. It will provide an effective way to backup the Asterisk PBX when undesirable changes are detected (often when Asterisk fails or power-off of the system).
FD140 is controlled through an Asterisk loadable module res_failover.so. This module keeps sending “running” signal to redundant server when Asterisk is running. Once Asterisk is down or system power is cut off, the module will not be able to send out the “running” signal to FD140 and thus FD140 will automatically switch to the redundant server.